<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="../js/jquery-1.8.3.js"></script>
    <script>
        //
        $(function () {
            let buttons = $('button');
            for (let i = 0; i < buttons.length; i++) {
                let button = buttons[i];
                alert(button)
            }
            alert(buttons);
            alert(document.getElementsByTagName('button'));
        })
    </script>
</head>
<body>
    <button></button>
    <button></button>
    <button></button>
</body>
</html>